Method of positioning plate cylinders in a multi-color rotary printing machine

ABSTRACT

A method for ascertaining possible register errors and for correcting the positioning of printing plate cylinders in a multi-color rotary printing machine utilizes geometric and regular figures of different sizes as register marks images. These figures, such as circles or squares are printed into each other and the resulting register marks&#39; prints may be analyzed to provide infotmaion useable to correct register errors in both the X and Y distances.

FIELD OF THE INVENTION

The present invention is directed generally to a method of positioningprinting plate cylinders in a multi-color rotary printing machine. Moreparticularly, the present invention is directed to a method forpositioning plate cylinders in a multicolor rotary printing machine byusing register marks. Most specifically, the present invention isdirected to a method for positioning plate cylinders in a multi-colorrotary printing machine using register marks on each plate cylinder withthese register marks being arranged to form regular geometric figures asregister marks prints on the print carrier. These regular geometricfigures may be concentric circles or squares and facilitate themeasurement of the distances between adjacent register marks so thatthese distances may be analyzed by suitable electric image detectingdevices. Once the positions of the register marks prints have beenmeasured and analyzed, the printing plates can be adjusted, ifnecessary, to correct register errors.

DESCRIPTION OF THE PRIOR ART

It has become generally known in the art to utilize various televisioncameras and associated video devices to evaluate printed products. Thepublication "Technische Vortrage 1971" or Technical Speeches 1971,published by the Deutsche Forschungsgesellschaft fur Druck-undReproductionstechnik e.v., or the German Research Company for Printingand Reproduction Technology provided an essay entitled "Application ofTV-Picture Evaluation for Measuring Tasks of the Printing Technology".This essay discussed the use of a video signal from a TV camera toevaluate printed products. It is further generally known in the art tooptically enlarge various video pictures so that a picture element to beevaluated will be cut by a sufficient number of TV-lines.

In the German published unexamined patent application No. 31 38 689there is disclosed a device for the detection of picture copies by usinga video camera as the detection device. In this application, the camerais a vidicon or so-called CCD-camera and may be equipped with a zoomobjective lens. In another German published unexamined patentapplication No. 24 55 973 there is described an optical charactersearching device in which the video signal may be digitized.

In PCT Application No. WO 86/05141 there is disclosed a process and adevice for the execution of the process which is useable with amulti-color rotary printing machine to position the various platecylinders of the printing machine with respect to each other. This isaccomplished by utilizing deviations of one register mark with respectto each other. This is accomplished by using a video camera to record agroup of marks printed on the print carrier and to form an image of thisgroup of marks. This image is then converted into a numerical imagewhich may be compared with an "analysis window". The "analysis window"consists of a reference point to which is associated a mark on theprinting carrier.

A disadvantage of the above-discussed process is that the ink registermarks are provided as points with a diameter of approximately 1 mm withthese points being arranged as corner points of an imaginary squarehaving an edge length of approximately 10 mm. This type of registerpoints are difficult to detect electronically. Defects on the printingcarrier itself in the area adjacent or within the square of registermarks could erroneously be analyzed as register point by the electronicsystem. Additionally, for point-shaped register marks, a leading,additional, bar-shaped trigger register mark is required. Furthermore,the position of each point to each other point must be calculated inboth the X- and Y- directions. If the electronic system fails, it isquite difficult for the printer to visually recognize the registerdeviation of the marks as they can be separated from each other by adistance of up to 10 mm and more. Due to the large distance between thecolor register marks, it is impossible to measure the distances betweenthe marks by using a measuring microscope. As the color register pointsare located on different levels from each other, the different distanceshave to be calculated first for the display on the screen. Moreover, inthe process disclosed in this prior art material, the whole "analysiswindow" must be analyzed. That means that a computer with a largecapacity is required if one wants to keep the analysis time short.Alternatively, one may use a smaller computer and accept a longeranalysis time Because of this relatively long analysis time, theapplication of this process is not overly appropriate for fast-runningrotary web-fed printing machines which may have a web speed of 15 m/secor more.

While the prior art discloses the general concept of using various marksand video cameras to measure the registry of printing plates in amulti-color press assembly, these prior art processes have requiredsignificant computer capabilities, substantial time, and have beendifficult to use in the absence of electronic signal processingequipment. Thus there is a need for a more practical and easily useableprocess. The method for positioning printing plate cylinders in amulti-color rotary printing machine in accordance with the presentinvention provides such a process and is a significant advance in theart.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method ofpositioning plate cylinders in a multi-color rotary printing machine.

Another object of the present invention is to provide a method ofmeasuring ink registry in both longitudinal and side register onmulti-color rotary printing machines.

A further object of the present invention is to provide a method ofmeasuring ink registry on multi-color rotary printing machines using anink video camera.

Still another object of the present invention is to provide a method formeasuring ink registry in multi-color rotary printing machines and todetermine deviations from a set value.

Yet a further object of the present invention is to provide a method formeasuring ink registry in multi-color rotary printing machines withoutthe necessity of having to evaluate the total measuring window.

As will be discussed in greater detail in the description of thepreferred embodiment which is set forth subsequently, the method ofmeasuring registry and positioning plate cylinders in a multi-colorrotary printing machine in accordance with the present inventionutilizes a plurality of register marks, each of which is printed, as aregister mark print, onto the print carrier by successive ones of theindividual printing plates in the printing machine. These register marksprints form one of several regular geometric figures which have thinboundary lines and which, in the preferred configuration, provide eitherconcentric circles or rectangles. These geometric configurations can beanalyzed using electric image detecting devices, such as video cameras,and the distance between individual ones of the thin lines can bereviewed to provide an indication of the registry between individualprinting plates. It is not necessary to evaluate the complete array ofregister marks to obtain appropriate information regarding plateregistration errors. One of the primary advantages to be achieved by thepresent invention is that the deviation of the register marks to eachother can directly be measured both in the X- as well as in the Y-directions. Thus this deviation need not be calculated especially bymeans of computers. The register marks in accordance with the inventionare designed as regular, geometric figures, so that it is possible tocheck by means of software that only register marks and not possibledefects on the printing carrier itself are analyzed. It is also easilypossible for the press operator to visually check the position of theregister marks to each other on a screen. To accomplish this, it is onlynecessary for the operator to insert a scale in the X- and Y-directionsinto the image on the screen. It is also unnecessary to analyze thewhole "analysis window". As a rule, only the immediate surrounding fieldaround the center of the "analysis window" need be analyzed. Only inextreme cases must the whole "analysis window" be read digit for digitand analyzed.

By using the method of the present invention, the decision and theintroduction of adjusting procedures are made faster than was thesituation when using prior art methods, provided the same computercapacity. The method of positioning printing plate cylinders in amulti-color rotary printing machine in accordance with the presentinvention will thus be seen as providing superior registry determinationin less time and with less difficulty than was required by priormethods. As such the present method provides a substantial improvementover the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

While the novel feature of the method of positioning plate cylinders ina multi-color rotary printing machine in accordance with the presentinvention are set forth with particularity in the appended claims, afull and complete understanding of the invention may be had by referringto the detailed description of the preferred embodiment which is setforth subsequently, and as illustrated in the accompanying drawings, inwhich:

FIG. 1 is a top plan view of a schematically depicted four color rotaryweb-fed printing machine showing plate cylinders in accordance with thepresent invention;

FIG. 2 is a depiction of a first configuration of a plurality ofregister marks printed onto a print carrier in accordance with thepresent invention;

FIG. 3 is a depiction of a second configuration of a plurality ofregister marks; and

FIG. 4 is a schematic depiction of an overall measuring assembly inaccordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As was set forth in the Description of the Prior Art portion of thepresent application, the PCT patent application WO 86/05141 disclosesand describes how color register marks for a multi-color print on aprint carrier, such as for example a paper web, may be printed out thendetected for analysis by a video camera. The analysis may be conductedby a suitable computer, again as discussed in this prior art patent.Furthermore, the positioning of the register marks on the print carrieris also discussed generally in this prior art. It will thus beunderstood that it is not necessary to discuss the overall multi-colorprinting process or the specific means to adjust plate cylinders intheir longitudinal axis direction and around their longitudinal axis.These are acknowledged as prior art and do not form a part of thepresent invention.

Referring now initially to FIG. 1, there may be seen a printing carrier1 which passes through four sequentially positioned printing units 2, 3,4 and 6. Each of these printing units 2, 3, 4 and 6 consists, in agenerally known manner, of an impression cylinder, a blanket cylinder, aplate cylinder and an inking unit. In this schematic drawing there areonly depicted the four plate cylinders 7, 8, 9 and 11 with theirassociated printing plates 12, 13, 14 and 16, as seen in the printcarrier running direction.

Each color to be printed by the multi-color printing machine has its ownprinting cylinder and associated printing plate. Furthermore, eachprinting plate has its own individual register mark associated with it.Thus, to accomplish four color printing of print carrier 1 there arerequired the four printing plates 12, 13, 14 and 16, as shown in FIG. 1.While the method in accordance with the present invention willhereinafter be discussed using a four color printing press, it will beapparent that printing presses using greater or fewer than four colorsare also contemplated by the invention.

Again referring to FIG. 1, each of the four printing plates 12, 13, 14,and 16 is provided with a register mark image 17, 18, 19 and 21respectively and each applies, according to the corresponding coloring,in the order black-blue-red-yellow, prints 17', 18', 19' and 21' on theprinting carrier 1, 17' is printed in black, 18' is printed in blue, 19'is printed in red and 21' in yellow. The register marks' images 17, 18,19 and 21 and thus the register marks' prints 17', 18', 19' and 21' aredesigned as regular figures preferably as closed squares or circles.Their printed lines are approximately 0.01-0.05 mm wide. All fourregister marks' images 17, 18, 19 and 21 have different sizes from eachother, so that their, for example, diameters are different from one theother, as may be seen in FIGS. 2 and 3. In practice, the dimensions ofthe register marks' images on their respective printing plates will beselected so that in the ideal situation in which there is no registererrors, four register marks' images 17, 18, 19 and 21 will printconcentrically into each other so that, as may be seen in FIGS. 2 and 3the distances "X" and the distances "Y" between the concentricallyplaced and similarly shaped register marks' prints 17; 18', 19' and 21'will be spaced from each other by a distance of generally about 2.0 mm.If the several printing plates 12, 13, 14, and 16 are not in properregistry with each other the register marks' prints 17', 18', 19', and21' will no longer be in concentric registry, as seen in FIGS. 2 and 3.In this situation, the distances "X" and "Y" will no longer be the samefrom one line to the next and this will provide a clear indication of aregistration error.

Turning now to FIG. 4, in conjunction with FIGS. 2 and 3, an imagedetecting device generally at 22 may be used to measure the deviationsof the register marks' 17', 18', 19', and 21' to each other in their "X"and "Y" directory. This image detecting device 22 may be of the generaltype discussed in the prior German published unexamined patentapplication No. 31 88 699 and the PCT application WO 86/05141. Thedeviations measured, such as X₁, X₂, X₃, and Y₁, Y₂, Y₃ for a four-colorprinting are then fed, as real values, to a control system for therotation of the plate cylinders 7, 8, 9 and 11 to each other in acircumferential direction to effect longitudinal register, and for thedisplacement in an axial direction. These real values are compared withsetpoint values, such as once x, twice x, three times x, once y, twicey, three times y, out of which adjusting values are created. Adjustingdevices 24, 26, 27, 28 on the plate cylinders 7, 8, 9 and 11 are thenused so that the plate cylinders 7 to 11 are adjusted to each other incircumferential and/or longitudinal axis directions. These adjustmentswill thus correct the registration errors shown by the register marks'prints 17', 18', 19' and 21.

The corrections of the distances within one set 17', 18', 19' and 21' ofregister marks' prints may be electronically measured in both the "X"and "Y" directions and these distances may be referenced to theinnermost register marks' print 17'. This will allow one to obtain thedistances, x₁, x₂, x₃ of the register marks' prints 18', 19' and 21'from the innermost register marks' print 17' the x direction, as is seenin FIGS. 2 and 3. Similarly, the distances y₁, y₂, y₃, of the registermarks' prints 18', 19' and 21' from the innermost register marks' print17' in the Y direction may be obtained. These measurements may becontinuously carried out for each printing multi-color printed imagesince, besides each multi-color printed image, there are also printedthe four register marks' prints 17', 18', 19' and 21' which are in theform of boundary lines of circles or squares that have been printed intoeach other and which are of different sizes. These circles of squaresthus only cut or contact themselves if there are longitudinal or sideregister faults.

Turning now primarily to FIG. 4, once the total register marks' prints17' to 21' for one printed image of the multi-color prints,respectively, are printed in a provided area on the printing carrier 1,their positions in the X- and Y- coordinate system are continuouslydetected in the X- and Y- directions by a video camera 22 during therunning of the printing carrier 1. The distances x₁, x₂, x₃ in the X-axis direction and y₁, y₂, y₃ in the Y- axis direction from the boundaryof the smallest register marks' prints 18', 19', 21' are electronicallymeasured. These values are continuously compared with setpoint valuesand each difference value is continuously converted into an adjustingvalue for each plate cylinder 7, 8, 9, and 11; and for each plate 12,13, 14, 16 by means of a regulating device in order to rotate theindividual plate cylinders 7, 8, 9, 11 in their longitudinal axisdirection and/or in the circumferential direction in or against theirrotary direction. Plate adjusting devices 24, 26, 27, 28 are knowngenerally and form no part of the present application.

While a preferred embodiment of a method for positioning plate cylindersin a multi-color rotary printing machine in accordance with the presentinvention has been set forth fully and completely hereinabove, it willbe apparent to one of skill in the art that a number of changes in, forexample, the number of printing plates and plate cylinders used, thetype of video camera and signal processing equipment, the type of plateshifting assemblies and the like may be made without departing from thetrue spirit and scope of the subject invention which is accordingly tobe limited only by the following claims.

What is claimed is:
 1. A method of positioning plate cylinders in amultiple color rotary printing machine usable for printing a multiplecolor image on a print carrier, said method comprising:providing a firstregister mark image on a first plate cylinder of a first color printingunit; forming said first register mark image as a closed regulargeometric shape having thin lines and having a first size; providing asecond register mark image on a second plate cylinder of a second colorprinting unit; forming said a second register mark image having saidclosed regular geometric shape having thin lines and having a secondsize, said second size of said second register mark image beingdifferent than said first size of said first register mark image;providing a plurality of successive register mark images on successiveplate cylinders of successive color printing units; forming each ofsuccessive register mark images as said closed regular geometric shapeof said first and second register mark images, each of said successiveregister mark images having thin lines and having a size which isdifferent than said first and second sizes of said first and secondregister mark images and from sizes of other ones of said successiveregister mark images; providing a separate one of said first, second,and successive register mark images for each color to be printed in amultiple color printing machine; passing said print carrier through eachof said first, second, and successive color printing units; contactingeach of said first, second, and successive closed regular geometricshaped, thin lined and different sized register mark images with saidprint carrier as said print carrier passes through said first, second,and successive color printing units; printing first, second, andsuccessive register mark prints on said print carrier corresponding tosaid first, second, and successive register mark images; forming aplurality of similar concentric closed regular geometric figures on saidprint carrier, each of said concentric closed regular geometric figureshaving one of said first, second, and successive register mark prints;detecting the position of each of said register mark prints in aselected one of said concentric closed regular geometric figures byusing an image detecting device; measuring relative distances betweenadjacent ones of said register mark prints in a selected one of saidconcentric closed regular geometric figures in X and Y axis directions;converting said measured relative distances into adjusting values usablefor adjusting relative positions of plate cylinders; and positioning oneof said first, second, and successive plate cylinders using saidadjusting values and obtaining proper color register of said first,second, and successive printing plates in said multiple color rotaryprinting machine.
 2. The method of claim 1 including the step ofproviding said register mark prints in each of said closed regulargeometric figures as squares of successively larger sizes.
 3. The methodof claim 1 including the step of providing said register mark prints ineach of said closed regular geometric figures as circles of successivelylarger sizes.